is there a way to select just the outer surface but not the inner?
You probably have got the nonmanifold elements there. Select the whole mesh in Edit Mode (A), go to Select-->NonMannifold, then delete the edges.


You may also use a MeshLint add on to do it. Activate it in User Preferences (Ctrl+Alt+U). Go to the MeshLint panel of the Data header, check the NonManifold Elements checkbox and click Select Lint button.